Joining of hybrid semi-finished products from sheet metal by orbital forming

Contrary demands like a reduction of carbon dioxide emissions and an increase in functionality are facing the manufacturing industry with growing challenges. When processing functional components, like synchronizer rings, conventional process chains, like shearing and subsequent joining, are reaching their limits due to an increased complexity of the components and a lack in efficiency, referring to the long process time. To meet these challenges, the strategy of lightweight construction combines the application of lightweight materials with efficient manufacturing processes and an innovative product design. One possibility within lightweight construction is the utilization of load-adapted hybrid components, featuring different material strength classes. In previous research, the process of orbital forming is used to manufacture semi-finished products with a varying thickness profile due to the specific radial material flow. This material flow should now be used to realize a permanent joint between materials of two different strength levels. Therefore, the process of orbital forming is modified to manufacture hybrid semi-finished products from a dual-phase steel DP600 and a naturally rigid aluminum alloy EN AW 5754, both with an initial thickness of 2.0 mm. Different joint geometries are cut by laser into a steel ring and the part is coaxially positioned around a basic aluminum disc inside a die and subsequently formed. The joint is investigated regarding the geometrical and mechanical properties, comparing a radial cross-section and the micro hardness distribution. In order to reveal the potential of orbital forming for a combined forming and joining operation, the axial as well as the peeling strength of the multi-material components are investigated and evaluated.

Deformation Characteristics and Microstructure Analysis of Aluminum Alloy Component with Complex Shape by Cold Orbital Forming

This work aimed to study the deformation characteristics and microstructure of AA6063 aluminum alloy component with complex shape manufactured by cold orbital forming processing. The material flowing behavior was analyzed by Finite Element (FE) simulation and forming experiments were carried out using bar blank with different lengths. The microstructure of the boss zone cut from the formed samples was observed using scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD). FE simulation and experiment results both showed the aluminum base can be formed using cold orbital forming process. The distributions of the effective strain of the component with different blank lengths were almost the same, and the effective strain was bigger at the boss and the flash as the forming finished. The material flow is complex, especially in the boss, and the folding defect was observed at the root of the boss. The distribution of Mg2Si strengthening precipitate is more homogeneous in the matrix, has a different shape, and shows directivity at different position of boss zone. The grains are elongated, and the extent is different at different positions of the boss zone after cold orbital forming, and the crystal orientation discrepancy is smaller in the component main body and bigger in the boss zone. Subsequent forming process and blank optimization need to be further researched to improve forming quality.

Maßgeschneiderte Halbzeuge*/Tailored Blanks – Manufacturing of functional parts for the realization of lightweight components

Die Blechmassivumformung erlaubt die effiziente Herstellung von leichtbaugerechten Funktionsbauteilen mit verschiedenartigen Nebenformelementen in einem kombinierten einstufigen Tiefzieh- und Stauchprozess. Durch die Analyse der Umformergebnisse mit konventionellem Halbzeug anhand von Gefügeschliffbildern und Härtemessungen lassen sich Bauteilfehler in Form von Falten und Rillen identifizieren. Diese lassen sich größtenteils auf einen dreiachsigen Spannungs- und Dehnungszustand sowie eine inadäquate Formfüllung zurückführen. Eine signifikante Verbesserung der Bauteilqualität kann durch den Einsatz von maßgeschneiderten Halbzeugen in der untersuchten Prozesskette ermöglicht werden. Durch die Herstellung der Halbzeuge in einem Taumelprozess kann eine gezielte Materialvorverteilung erfolgen, welche die Formfüllung deutlich erhöhen und in Folge dessen die auftretenden Bauteilfehler reduzieren kann. Aktuelle Forschungsarbeiten am Lehrstuhl für Fertigungstechnologie beschäftigen sich demnach mit der Erweiterung des Einsatzbereichs von maßgeschneiderten Halbzeugen.   Sheet Bulk Metal Forming enables the efficient manufacturing of functional lightweight components with different functional elements in a combined single stage deep drawing and upsetting process. By investigating the forming results with a conventional blank, regarding the properties like grain structure and Vickers hardness distribution, process limitations such as buckling and folding can be detected. These failures occur due to a three-dimensional stress and strain state as well as an insufficient die filling. A significant improvement of the quality of the produced parts can be enabled by the use of Tailored Blanks in the investigated process chain. With the manufacturing of the semi-finished parts by orbital forming, an adapted material pre-distribution can be realized, thus improving the die filling followed by a decrease of the parts’ failures. Current research at the Institute of Manufacturing Technology focuses on the extension of the applicability of Tailored Blanks.

Ultrasonic Orbital Microforming—A New Possibility in the Forming of Microparts

The demand for very small metal parts is growing rapidly due to the development of micromechanisms. In microtechnology, the dimensions of scale parts are below 1 + c mm, where c varies based on the process type. The “classic” processes usually cannot be simply scaled down, and tools require thorough structural changes. Microforming has been isolated from the area of “classic” metal forming and is governed by modified laws. The proposed new technological process ultrasonic orbital microforming (UOM) and its related phenomena are possible only on a microscale. UOM is a process that uses the broadly understood idea of orbital forging, which involves rolling on a closed road. This, however, is where the analogy ends. The UOM process uses completely different laws of physics. The process, the result of which is the axial-symmetrical micropart, consists of inducing a fast rotational movement of the billet by a punch that is vibrating at an ultrasonic frequency. The rotational speed is so fast that gyroscopic effect plays an important role. This work presents the concept of the process, preliminary research results, and their general interpretation. FEM-3d modeling of micro-orbital forming processes in geometrically similar conditions to the UOM process was also performed, obtaining shapes consistent with those obtained in the UOM.

Fortpflanzung von Unsicherheit in Prozessketten*/Propagation of uncertainty in process chains consisting of forming and machining operations

Aufeinanderfolgende Umform- und Zerspanungsprozesse stellen im industriellen Umfeld eine typische Wertschöpfungskette dar. Die Auswirkungen von Unsicherheit werden in solchen Prozessketten bislang nur in Einzelprozessen untersucht. Gegenstand der Untersuchungen im Sonderforschungsbereich 805 ist die Entwicklung einer verketteten, geregelten Prozesskette über die unterschiedlichen Bearbeitungsoperationen hinweg. In einem ersten Schritt wird im Rahmen dieses Aufsatzes die Verkettung eines Taumelprozesses mit einer nachfolgenden Reiboperation in einer Simulation untersucht. Die Geometrie der umgeformten Bauteile wird dazu mittels einer entwickelten Schnittstelle in ein passendes Format umgewandelt. Bei der Simulation der Reibbearbeitung wird der Einfluss der Schneidengeometrie sowie unterschiedlicher Bearbeitungsstrategien auf die Auslenkung des Werkzeuges untersucht.   Successive forming and machining processes represent a common industrial value chain. By now, the effect of uncertainty on these process chains has solely been examined with regard to single processes. The research subject of the Collaborative Research Centre 805 is the development of an interlinked closed-loop controlled process chain consisting of various processing operations. This paper presents the investigation results of an orbital forming process simulation succeeded by a reaming operation. An interface has been designed that converts the geometry of the formed part into a suitable format for the subsequent reaming process simulation. By means of the coupled simulation the influence of cutting edge geometry and machining strategies on tool deflection is examined.

Research on Cold Orbital Forming of Complex Sheet Metal of Aluminum Alloy

This study aims at exploring the potentialities of cold orbital forming in forming complex sheet metal. Aiming at a complex mobile phone shell component of aluminum alloy, two technical schemes for cold orbital forming are first presented. Then, the optimized one, i.e., the more complex inner surface of mobile phone shell is arranged to be formed by the rocking punch with a complex motion, is determined by analyzing the nonuniform plastic deformation laws and punch filling behaviors. On the basis of the optimized technical scheme, the blank geometry in cold orbital forming of mobile phone shell is also optimized based on the forming status of the most difficult forming zone. The consistent finite element (FE) simulated and experimental results indicate that under the optimized technical scheme, not only the bosses in the mobile phone shell are fully formed but also the obtained flow lines are reasonable, which proves that the technical scheme presented in this study is feasible and cold orbital forming exhibits huge potentialities in forming complex sheet metal.